BACKGROUND/AIMS: Visually guided saccades and gaze-fixation ability were recorded in patients with early Parkinson's disease (PD). METHODS: Magnetic search coil system was used to measure horizontal and vertical eye positions. RESULTS: 'Staircase' visually guided saccades (multiple hypometric saccades separated by an intersaccadic interval) and 'staircase' square-wave jerks (SWJ) were present in all patients. The SWJ amplitude (total amplitude of the series of hypometric saccades comprising the SWJ) was abnormally large (mean 2°). SWJ frequency was also abnormally high (50-70 intrusions/min). CONCLUSION: Loss of dopaminergic neurons in the substantia nigra pars compacta leading to phasic excitation of the substantia nigra pars reticulata and, in turn, phasic inhibition of the superior colliculus (SC), may account for 'staircase' visually guided saccades in these patients. This mechanism, however, does not explain abnormally large SWJ, which in the traditional view results from decreased inhibition upon SC. The abnormally large SWJ could be due to a compensatory increase in frontal eye field activity secondary to the increased inhibition upon the SC. Abnormally large and frequent SWJ are often used clinically to distinguish multi-system atrophy from idiopathic PD. Our study, however, suggests that idiopathic PD cannot be excluded if the patient has large-amplitude SWJ.
BACKGROUND/AIMS: Visually guided saccades and gaze-fixation ability were recorded in patients with early Parkinson's disease (PD). METHODS: Magnetic search coil system was used to measure horizontal and vertical eye positions. RESULTS: 'Staircase' visually guided saccades (multiple hypometric saccades separated by an intersaccadic interval) and 'staircase' square-wave jerks (SWJ) were present in all patients. The SWJ amplitude (total amplitude of the series of hypometric saccades comprising the SWJ) was abnormally large (mean 2°). SWJ frequency was also abnormally high (50-70 intrusions/min). CONCLUSION: Loss of dopaminergic neurons in the substantia nigra pars compacta leading to phasic excitation of the substantia nigra pars reticulata and, in turn, phasic inhibition of the superior colliculus (SC), may account for 'staircase' visually guided saccades in these patients. This mechanism, however, does not explain abnormally large SWJ, which in the traditional view results from decreased inhibition upon SC. The abnormally large SWJ could be due to a compensatory increase in frontal eye field activity secondary to the increased inhibition upon the SC. Abnormally large and frequent SWJ are often used clinically to distinguish multi-system atrophy from idiopathic PD. Our study, however, suggests that idiopathic PD cannot be excluded if the patient has large-amplitude SWJ.
Authors: Nicholas G Murray; Brian Szekely; Arthur Islas; Barry Munkasy; Russell Gore; Marian Berryhill; Rebecca J Reed-Jones Journal: J Neurotrauma Date: 2019-10-11 Impact factor: 5.269
Authors: Cecilia Bonnet; Jan Rusz; Marika Megrelishvili; Tomáš Sieger; Olga Matoušková; Michael Okujava; Hana Brožová; Tomáš Nikolai; Jaromír Hanuška; Mariam Kapianidze; Nina Mikeladze; Nazi Botchorishvili; Irine Khatiashvili; Marina Janelidze; Tereza Serranová; Ondřej Fiala; Jan Roth; Jonas Bergquist; Robert Jech; Sophie Rivaud-Péchoux; Bertrand Gaymard; Evžen Růžička Journal: PLoS One Date: 2014-08-12 Impact factor: 3.240